Control device for an intake valve or exhaust valve of an internal combustion engine

ABSTRACT

The invention relates to a control device for an intake valve or exhaust valve of an internal combustion engine comprising an adjusting element and a control element. According to the invention, the adjusting element comprises a base body ( 2 ) and is displaceably arranged between the control element and the valve. The control element rotates during the operation of the control device. Rotating control element circumferential areas with contours that vary in the circumferential direction are provided as control cams throughout the rotating control element. Force introduction areas KEB ( 6, 7 ), which are positioned in a non-uniform manner, and a force transfer area KUB ( 3 ) are provided on the base body ( 2 ) of the adjusting element. Switching means for the alternately contacting assignment of the KEB areas ( 6, 7 ) are provided on the different control cam areas of the control element. The aim of the invention is to enable the largest possible number of different controls for an engine valve. To this end, the invention provides that, in a control device of this type, the mutual assignment between the one KUB area ( 3 ) and the at least two KEB areas ( 6, 7 ) can be modified among one inside the adjusting element base body ( 2 ) by means of the switching means.

[0001] The invention relates to a control device for an intake orexhaust valve of an internal combustion engine according to the preambleof patent claim 1.

[0002] With such a control device, various valve controls can beswitched in relation to varying loads or motor brake operation forexample. Such devices of the most diverse embodiments are known, forexample, from DE 27 53 197 A1, DE 36 13 945 A1, DE 38 00 347 A1, DE 4136 143 A1, EP 0 775 225 B1, U.S. Pat. No. 5,544,626 and JP 6-88 512 A.

[0003] With all these devices where the control element is a cam shaft,the different contours of the control cams on the cam shaft have to fallinside each other, i.e. within an envelope curve which is determined bythe control curve of the control cam with the greatest sweep. Otherwise,these known devices cannot operate. In systems such as EP 0 458 857 B1for example, a switching between different control contours occurs suchthat in a control state with play, a standard control contour isobtained. In a further control state, the entire cam profile for thevalve motion available on the cam shaft is activated by removing theplay. The additional control contour is engaged while the standardcontour in such a system cannot be disengaged. The control contour isproportional to the entire envelope curve of the cam shaft. To theextent that, for the control device according to EP 0 775 225 B1, avalve control predetermined by the control curve of the control cam canbe varied in conjunction with a hydraulic unit, it is not possible toobtain any desired valve controls. Neither can the stroke of thestandard motion be disengaged.

[0004] Similar control devices with similar disadvantages and sometimeswith particularly complex design features are also also known from DE 3219 611 A1, FR 27 09 150 A1, FR 27 09 149 A1, U.S. Pat. No. 5,564,373, JP55-152308 U and from JP Patent Abstracts of Japan: 10077815 A, 07317081A, 0707719 A, 03179115 A, 02252910 A as well as 02095708 A.

[0005] The invention deals with the problem of providing a device withwhich the control of a valve can be varied in a range as large aspossible in order to be able to adapt in an optimum manner to differingengine conditions. Special consideration has been given to an effectiveengagement of a braking operation for an internal combustion engine.

[0006] An in principle solution of this problem presents a genericallyappropriate device with the characteristic features of claim 1.

[0007] Suitable embodiments are the subject of the dependent claims andare described in more detail in connection with the description ofembodiments.

[0008] The invention is based on the general idea of introducing,between control elements with differing control curves and the valve tobe controlled, an adjusting element whose points of engagement with thecontrol curves and the valve can be infinitely adjusted relative to eachother as desired in order to thus be able to set any desired, differingcorrelation. That way, any control settings can then be obtained in asimple manner. As a control element, a cam shaft with differing controlcurves can be used or several cam shafts with differing control curveseach can also be used. When using several cam shafts as a controlelement, the variability of the possible control settings is increased.Thus, especially cam shafts rotating at different speeds can be used.

[0009] Advantageously, hydraulic units are used as switching means. Theuse of hydraulic units has the advantage that the moment transfer rangesof the adjusting element relative to the control element, on the onehand, and/or the valve, on the other hand, can be integrated. Thus, thevalve play compensation measures, basically known for engine valvecontrols, can be integrated easily into these hydraulic units.

[0010] Advantageously, drag levers or rocker arms can be used asadjusting elements. It is also possible to use an adjusting elementcapable of linear motion only. Preferably, the force transfer takesplace at the end of a valve stem or, if several valves are beingoperated, onto an intermediate element such as a valve bridge.

[0011] Useful and advantageous embodiments of the invention arepresented in the drawing.

[0012] Shown are:

[0013]FIG. 1 a perspective view of a drag lever as a control element,

[0014]FIG. 2 a section through the drag lever along the line II-II inFIG. 1 with an additional view of a cam shaft controlling this draglever, in a first control state of the force introduction and transferareas of this drag lever,

[0015]FIG. 3 the drag lever in the view according to FIG. 2 in adifferent control position of the force introduction and transfer areas,

[0016]FIG. 4 a section through a rocker arm used as a control element inan arrangement between two cam shafts,

[0017]FIG. 5 a section through a adjusting tappet used as a controlelement in an arrangement between a cam shaft and a valve, not shown, ina first control position,

[0018]FIG. 6 the adjusting tappet in the view according to FIG. 5 in asecond control position of the force introduction and transfer areas.

[0019] Embodiment According to FIGS. 1 to 3

[0020] A cam shaft 1 used as a control element acts on a drag lever 2serving as an adjustment element, said drag lever in turn controllingthe motion of a valve, not shown, of an internal combustion engine. Theengine valve, not shown, is spring loaded such that the valve stem endis pushed against the drag lever 2 by the force of the valve spring. Inthe following, the term force transfer area (KUB) is used for the areaof the drag lever 2 with which the drag lever acts on the valve stemend, and it is referred to by reference number 3.

[0021] In axial direction, the cam shaft 1 has control contours 4, 5adjacent to, but different from each other. These control contours 4, 5correspond with contact areas on drag lever 2, which in the followingare referred to as force introduction areas (KEB) and which arepresented in the drawing as primary KEB area 6 and secondary KEB area 7.The primary KEB area 6 consists of rotatable primary roller 8 mounted ina fixed position within the drag lever 2.

[0022] The secondary KEB area 7 is formed by a rotatable secondaryroller 11 mounted within a tappet 9 of a hydraulic unit 10. The KUB area3 is integrated into a piston 12 of a further hydraulic unit 13. Thehydraulic units 10 and 13 are hydraulically connected via a hydrauliccontrol unit and via a connecting channel 14 (FIGS. 2, 3). Along theconnecting channel 14, there are hydraulic control valves (not shown inthe drawing) for activating hydraulic units for which the connectingchannel 14 is also connected with a hydraulic pressure source and acontrol line (not shown).

[0023] The drag lever 2 can pivot around a joint axis 15.

[0024] The control device described above operates as follows.

[0025] If the control curve 4 is required to be the controlling elementfor the valves, then tappet 9 with the secondary roller 11 are fullyretracted into hydraulic unit 10 and the piston 12 of the hydraulic unit13 is fully extended to a predetermined, set length and hydraulicallylocked. Due to the spring force acting on the valve stem of the enginevalve, the drag lever 2 contacts the control contour 4 of the cam shaft1 via the primary roller 8. Due to the piston 12 being hydraulicallylocked in the hydraulic unit 13, the engine valve is controlled via thedrag lever 2, in a first control position, by the control contour 4 ofthe cam shaft 1.

[0026] If the engine valve is to be controlled by the control contour 5of the cam shaft 1, then tappet 9 of the hydraulic unit 10 is moved to afully retracted setting with the aid of hydraulic control valves as aswitching means (not shown) and the piston 12 of the hydraulic unit 13is moved to a fully retracted setting. If tappet 9 and piston 12 arehydraulically locked in these positions, the drag lever 2 controls theengine valve according to control contour 5 which is in contact with thesecondary roller 11 of tappet 9. This control arrangement represents asecond control position when compared to the first control position ofthe drag lever described above.

[0027] Adjustment elements of engine valves driven by a cam shaftnormally have a so-called hydraulic valve play compensation. Such ahydraulic valve play compensation arrangement can easily be adopted forthe present version of adjustment elements, by being integrated into thehydraulic unit 10 and 13. This can be achieved by applying generallyknown technical knowledge so that it is not necessary here to providefurther technical explanations. In principle, for the describedhydraulic units 10 or 13, it is sufficient to remove the strokelimitation described.

[0028] Due to the variability of the position of the KUB area 3 withinthe drag lever 2, it is possible to adjust the KEB areas 6 and 7relative to each other such that these areas can follow differentcontrol contours 4 and 5 on the cam shaft 1 whereby one contour need notbe positioned within the other contour. This is an essential advantageof the device in terms of the invention. At any one time, only onecontrol contour drives the motion of the valve.

[0029] Embodiment According to FIG. 4

[0030] In this embodiment, when compared with the device in FIGS. 1 to3, functionally equivalent parts are given the same reference number.

[0031] In contrast to the embodiment in FIGS. 1 to 3, the embodimentaccording to FIG. 4 has two separate cam shafts 1, 1′ with two differentcontrol contours 4′ and 5′ respectively. Instead of the drag lever 2 inthe device described previously, a rocker arm 2′ is used here. All otherparts are equivalent so that a renewed description is not necessary.

[0032] The operation of the device according to FIG. 4 is as follows.

[0033] In a first control position of rocker arm 2′, equivalent to thepreviously described first embodiment, the engine valve control isdriven by the control contour 4′ of the cam shaft 1′ as one of the totalof two cam shafts. In this operating mode, the tappet 9—contrary to itsrepresentation in the drawing—is retracted in the hydraulic unit 10 sothat no contact occurs between this tappet 9 and the other cam shaft 1,i.e. during all rotary positions of the cam shaft 1. In this firstcontrol position, the piston 12 is fully extended.

[0034] In a second control position, which again is equivalent to thedevice according to FIGS. 1 to 3 and which is shown in FIG. 4, thetappet 9 of hydraulic unit 10 is fully extended and the piston 12 ofhydraulic unit 13 is fully retracted. In this control position, thecontrol emanating from rocker arm 2′ is based on the control contour 4′of cam shaft 1′.

[0035] The hydraulic valve play compensation arrangements normally partof control devices for engine valves, and mentioned previously already,can also be integrated into the hydraulic units 10 and 13 of thisembodiment by removing the stroke limitations for the hydraulic units.

[0036] The cam shafts 1 and 1′ can operate at different rotary speeds.

[0037] Embodiments According to FIGS. 5 and 6

[0038] In this embodiment, too, when compared with the device in FIGS. 1to 4, functionally equivalent parts are given the same reference number

[0039] Instead of a lever as in the versions described previously, anadjustment tappet 2″ is used in this embodiment as a control elementbetween cam shaft and valve.

[0040] The operation of this device is equivalent to that of theembodiment according to FIG. 2 with reference to FIG. 5 and that of FIG.3 with reference to FIG. 6 so that a renewed description is notnecessary.

1. A control device for at least one spring-loaded intake or exhaustvalve of an internal combustion engine with one adjustment element andat least one control element (2, 2′, 2″ and 1, 1′ respectively) in whichthe adjustment element (2, 2′, 2″) has a base body capable of motion andis located between at least one control element (1, 1′) and the valve,the at least one control element (1, 1′) rotates during the operation ofthe control device, through the at least one rotating control element(1, 1′), at least two rotating control element circumferential areas arepresent as control contours (4, 5) with differing contours around thecircumference, on the base body of the adjustment element (2, 2′, 2″)are provided at least two differently positioned force introductionareas KEB (6, 7) and one force transfer area KUB (3), the force transferarea (3) acts on the at least one engine valve, switching means areprovided for alternatively correlating the KEB areas (6, 7) to thediffering control curve areas (4, 5 ) of the control element (1, 1′) tobring them into contact, characterised in that within the adjustmentelement (2, 2′, 2″) base body, the correlation between the one KUB areaand the at least two KEB areas (6, 7) can be varied relative to eachother exclusively with the aid of switching means being located withinthe adjustment element (2, 2′, 2″) base body whereby all the controlcontours (4, 5) present on the control element (1, 1′) are exclusivelycorrelated with the KEB areas (6, 7) which can alternately be broughtinto engagement.
 2. The control device according to claim 1,characterised in that the switching means are hydraulically lockablehydraulic units (10, 13).
 3. The control device according to claim 2,characterised in that the KEB and/or the KUB areas (6, 7 and 3respectively) are each designed as a surface of hydraulically adjustableparts (9, 12) of the hydraulic units (10, 13).
 4. The control deviceaccording to claims 2 or 3, characterised in that valve playcompensation measures, basically known for engine valve controls, areintegrated in the hydraulic units (10, 13).
 5. The control deviceaccording to one of the previous claims, characterised in that at leasttwo control elements in the form of cam shafts (1, 1′) are provided. 6.The control device according to claim 5, characterised in that the atleast two cam shafts (1, 1′) rotate at different speeds during theoperation of the control device.